Publications by authors named "Ryan C McKellar"

24 Publications

  • Page 1 of 1

A new pan-kinosternid, Leiochelys tokaryki, gen. et sp. nov., from the late Maastrichtian Frenchman formation, Saskatchewan Canada.

Anat Rec (Hoboken) 2022 Jun 3. Epub 2022 Jun 3.

Department of Biology, University of Regina, Regina, Saskatchewan, Canada.

Previously, only a single member of Pan-Kinosternidae (Yelmochelys rosarioae) had been documented from the Late Cretaceous epoch. In this report we describe a new pan-kinosternid genus and species, herein named Leiochelys tokaryki, based on a nearly complete, articulated skeleton from the Late Cretaceous (Maastrichtian) Frenchman Formation of Saskatchewan, Canada. L. tokaryki differs most notably from the previously described Y. rosarioae in having triangular plastral lobes, and in that the suture between the hyo- and hypoplastron is in line with the suture between the fifth and sixth peripherals. A maximum parsimony analysis suggests that L. tokaryki is intermediate between Y. rosarioae and crown-group kinosternids. Kinosternid features present in L. tokaryki include the presence of a reduced plastral bridge that extends from the posterior tip of peripheral 4 to the anterior tip of peripheral 7, two inframarginals that contact one another, a smooth triturating surface, and participation of the palatine in the triturating surface. An unexpected feature of the skull is the presence of a large stapedial canal, suggesting that the decrease in size of the stapedial canal and increase in the canalis caroticus cerebralis occurred independently in Dermatemydidae and Kinosternidae. The character-states of the skull and skeleton of L. tokaryki indicate that morphological changes occurring during the diversification of Kinosternoidea were more complex than expected based on data from derived members of the group.
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http://dx.doi.org/10.1002/ar.24952DOI Listing
June 2022

First fossil representative of Cerylonidae (Coleoptera: Coccinelloidea) described using X-ray micro-computed tomography, from Eocene Baltic amber.

Zootaxa 2021 Sep 7;5032(2):225-236. Epub 2021 Sep 7.

Shirshov Institute of Oceanology, Russian Academy of Sciences, Nahimovskiy prospekt 36, Moscow, 117997, Russia. .

Based on material originating from five amber collections of Eocene Baltic amber, Protostomopsis pandema gen. et sp. nov. is described and illustrated using X-ray micro-computed tomography. It is the first formally described extinct species of Cerylonidae, and the first known Palaearctic representative of the subfamily Ostomopsinae. As such, the new species extends the temporal range of the family Cerylonidae by approximately 45 Ma.
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http://dx.doi.org/10.11646/zootaxa.5032.2.4DOI Listing
September 2021

The first described darkling beetle of the tribe Metaclisini (Coleoptera: Tenebrionidae) from Eocene Baltic amber.

Zootaxa 2021 Jul 12;4999(3):279-284. Epub 2021 Jul 12.

Institute of Life Sciences and Technologies, Daugavpils University, Vienbas iela 13, Daugavpils, LV-5401, Latvia..

The description of an extinct species of Metaclisa Jacquelin du Val, 1861 (Tenebrionidae) is presented. This genus and the tribe Metaclisini are recorded as fossils for the first time, from Eocene Baltic amber. The new species Metaclisa ottoi sp. nov. belongs to the subgenus Trichometaclisa subgen. nov. and differs from all other Metaclisini in possessing short, fine recumbent setation on the pronotum and elytra; in addition, the prosternal process in Metaclisa ottoi sp. nov. is roundly bent down and weakly projected behind the procoxae, which differs from extant species.
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http://dx.doi.org/10.11646/zootaxa.4999.3.7DOI Listing
July 2021

Crab in amber reveals an early colonization of nonmarine environments during the Cretaceous.

Sci Adv 2021 Oct 20;7(43):eabj5689. Epub 2021 Oct 20.

Royal Saskatchewan Museum, Regina, SK S4P 4W7, Canada.

Amber fossils provide snapshots of the anatomy, biology, and ecology of extinct organisms that are otherwise inaccessible. The best-known fossils in amber are terrestrial arthropods—principally insects—whereas aquatic organisms are rarely represented. Here, we present the first record of true crabs (Brachyura) in amber—from the Cretaceous of Myanmar [~100 to 99 million years (Ma)]. The new fossil preserves large compound eyes, delicate mouthparts, and even gills. This modern-looking crab is nested within crown Eubrachyura, or “higher” true crabs, which includes the majority of brachyuran species living today. The fossil appears to have been trapped in a brackish or freshwater setting near a coastal to fluvio-estuarine environment, bridging the gap between the predicted molecular divergence of nonmarine crabs (~130 Ma) and their younger fossil record (latest Cretaceous and Paleogene, ~75 to 50 Ma) while providing a reliable calibration point for molecular divergence time estimates for higher crown eubrachyurans.
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http://dx.doi.org/10.1126/sciadv.abj5689DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8528423PMC
October 2021

Retraction Note: Hummingbird-sized dinosaur from the Cretaceous period of Myanmar.

Nature 2020 08;584(7822):652

Beijing Advanced Sciences and Innovation Center, Chinese Academy of Sciences, Beijing, China.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41586-020-2553-9DOI Listing
August 2020

Hummingbird-sized dinosaur from the Cretaceous period of Myanmar.

Nature 2020 03 11;579(7798):245-249. Epub 2020 Mar 11.

Beijing Advanced Sciences and Innovation Center, Chinese Academy of Sciences, Beijing, China.

Skeletal inclusions in approximately 99-million-year-old amber from northern Myanmar provide unprecedented insights into the soft tissue and skeletal anatomy of minute fauna, which are not typically preserved in other depositional environments. Among a diversity of vertebrates, seven specimens that preserve the skeletal remains of enantiornithine birds have previously been described, all of which (including at least one seemingly mature specimen) are smaller than specimens recovered from lithic materials. Here we describe an exceptionally well-preserved and diminutive bird-like skull that documents a new species, which we name Oculudentavis khaungraae gen. et sp. nov. The find appears to represent the smallest known dinosaur of the Mesozoic era, rivalling the bee hummingbird (Mellisuga helenae)-the smallest living bird-in size. The O. khaungraae specimen preserves features that hint at miniaturization constraints, including a unique pattern of cranial fusion and an autapomorphic ocular morphology that resembles the eyes of lizards. The conically arranged scleral ossicles define a small pupil, indicative of diurnal activity. Miniaturization most commonly arises in isolated environments, and the diminutive size of Oculudentavis is therefore consistent with previous suggestions that this amber formed on an island within the Trans-Tethyan arc. The size and morphology of this species suggest a previously unknown bauplan, and a previously undetected ecology. This discovery highlights the potential of amber deposits to reveal the lowest limits of vertebrate body size.
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http://dx.doi.org/10.1038/s41586-020-2068-4DOI Listing
March 2020

A direct association between amber and dinosaur remains provides paleoecological insights.

Sci Rep 2019 11 29;9(1):17916. Epub 2019 Nov 29.

Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.

Hadrosaurian dinosaurs were abundant in the Late Cretaceous of North America, but their habitats remain poorly understood. Cretaceous amber is also relatively abundant, yet it is seldom found in direct stratigraphic association with dinosaur remains. Here we describe an unusually large amber specimen attached to a Prosaurolophus jaw, which reveals details of the contemporaneous paleoforest and entomofauna. Fourier-transform Infrared spectroscopy and stable isotope composition (H and C) suggest the amber formed from resins exuded by cupressaceous conifers occupying a coastal plain. An aphid within the amber belongs to Cretamyzidae, a Cretaceous family suggested to bark-feed on conifers. Distinct tooth row impressions on the amber match the hadrosaur's alveolar bone ridges, providing some insight into the taphonomic processes that brought these remains together.
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http://dx.doi.org/10.1038/s41598-019-54400-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6884503PMC
November 2019

A mid-Cretaceous enantiornithine foot and tail feather preserved in Burmese amber.

Sci Rep 2019 10 29;9(1):15513. Epub 2019 Oct 29.

Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, Yunnan, 650091, China.

Since the first skeletal remains of avians preserved in amber were described in 2016, new avian remains trapped in Cretaceous-age Burmese amber continue to be uncovered, revealing a diversity of skeletal and feather morphologies observed nowhere else in the Mesozoic fossil record. Here we describe a foot with digital proportions unlike any previously described enantiornithine or Mesozoic bird. No bones are preserved in the new specimen but the outline of the foot is recorded in a detailed skin surface, which is surrounded by feather inclusions including a partial rachis-dominated feather. Pedal proportions and plumage support identification as an enantiornithine, but unlike previous discoveries the toes are stout with transversely elongated digital pads, and the outer toe appears strongly thickened relative to the inner two digits. The new specimen increases the known diversity and morphological disparity among the Enantiornithes, hinting at a wider range of habitats and behaviours. It also suggests that the Burmese amber avifauna was distinct from other Mesozoic assemblages, with amber entrapment including representatives from unusual small forms.
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http://dx.doi.org/10.1038/s41598-019-51929-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6820775PMC
October 2019

A New Enantiornithine Bird with Unusual Pedal Proportions Found in Amber.

Curr Biol 2019 07 11;29(14):2396-2401.e2. Epub 2019 Jul 11.

Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.

Recent discoveries of vertebrate remains trapped in middle Cretaceous amber from northern Myanmar [1, 2] have provided insights into the morphology of soft-tissue structures in extinct animals [3-7], in particular, into the evolution and paleobiology of early birds [4, 8, 9]. So far, five bird specimens have been described from Burmese amber: two isolated wings, an isolated foot with wing fragment, and two partial skeletons [4, 8-10]. Most of these specimens contain the remains of juvenile enantiornithine birds [4]. Here, we describe a new specimen of enantiornithine bird in amber, collected at the Angbamo locality in the Hukawng Valley. The new specimen includes a partial right hindlimb and remiges from an adult or subadult bird. Its foot, of which the third digit is much longer than the second and fourth digits, is distinct from those of all other currently recognized Mesozoic and extant birds. Based on the autapomorphic foot morphology, we erect a new taxon, Elektorornis chenguangi gen. et sp. nov. We suggest that the elongated third digit was employed in a unique foraging strategy, highlighting the bizarre morphospace in which early birds operated.
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http://dx.doi.org/10.1016/j.cub.2019.05.077DOI Listing
July 2019

A new fossil species of Pycnomerus Erichson (Coleoptera: Zopheridae) from Baltic amber, and a replacement name for a Recent North American congener.

Zootaxa 2019 Jan 29;4550(4):565-572. Epub 2019 Jan 29.

Institute of Life Sciences and Technologies, Daugavpils University, Vienības 13, Daugavpils, LV-5401, Latvia..

Based on a well-preserved specimen from Eocene Baltic amber, the second fossil species belonging to the genus Pycnomerus Erichson (Coleoptera: Zopheridae: Zopherinae), P. agtsteinicus Bukejs, Alekseev McKellar sp. nov. is described and illustrated using synchrotron X-ray micro-CT observations. The new species adds to the sparse fossil record of Pycnomerus, which consists of the Baltic amber discoveries, and only four subfossil records in sediments that are less than one million years old. As part of this work, the new replacement name Pycnomerus lordi Bukejs, Alekseev McKellar nom. nov. is also established for the extant species Pycnomerus sulcicollis LeConte, 1863 [non Pycnomerus sulcicollis (Germar, 1824)].
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http://dx.doi.org/10.11646/zootaxa.4550.4.6DOI Listing
January 2019

A fully feathered enantiornithine foot and wing fragment preserved in mid-Cretaceous Burmese amber.

Sci Rep 2019 01 30;9(1):927. Epub 2019 Jan 30.

Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, CA, 90007, USA.

Over the last three years, Burmese amber (~99 Ma, from Myanmar) has provided a series of immature enantiornithine skeletal remains preserved in varying developmental stages and degrees of completeness. These specimens have improved our knowledge based on compression fossils in Cretaceous sedimentary rocks, adding details of three-dimensional structure and soft tissues that are rarely preserved elsewhere. Here we describe a remarkably well-preserved foot, accompanied by part of the wing plumage. These body parts were likely dismembered, entering the resin due to predatory or scavenging behaviour by a larger animal. The new specimen preserves contour feathers on the pedal phalanges together with enigmatic scutellae scale filament (SSF) feathers on the foot, providing direct analogies to the plumage patterns observed in modern birds, and those cultivated through developmental manipulation studies. Ultimately, this connection may allow researchers to observe how filamentous dinosaur 'protofeathers' developed-testing theories using evolutionary holdovers in modern birds.
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http://dx.doi.org/10.1038/s41598-018-37427-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353931PMC
January 2019

A mid-Cretaceous embryonic-to-neonate snake in amber from Myanmar.

Sci Adv 2018 07 18;4(7):eaat5042. Epub 2018 Jul 18.

Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.

We present the first known fossilized snake embryo/neonate preserved in early Late Cretaceous (Early Cenomanian) amber from Myanmar, which at the time, was an island arc including terranes from Austral Gondwana. This unique and very tiny snake fossil is an articulated postcranial skeleton, which includes posterior precloacal, cloacal, and caudal vertebrae, and details of squamation and body shape; a second specimen preserves a fragment of shed skin interpreted as a snake. Important details of skeletal ontogeny, including the stage at which snake zygosphene-zygantral joints began to form along with the neural arch lamina, are preserved. The vertebrae show similarities to those of fossil Gondwanan snakes, suggesting a dispersal route of Gondwanan faunas to Laurasia. Finally, the new species is the first Mesozoic snake to be found in a forested environment, indicating greater ecological diversity among early snakes than previously thought.
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http://dx.doi.org/10.1126/sciadv.aat5042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6051735PMC
July 2018

A gigantic marine ostracod (Crustacea: Myodocopa) trapped in mid-Cretaceous Burmese amber.

Sci Rep 2018 01 22;8(1):1365. Epub 2018 Jan 22.

State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing, 100083, China.

The mid-Cretaceous Burmese amber (~99 Ma, Myanmar), widely known for exquisite preservation of theropods, also yields microfossils, which can provide important contextual information on paleoenvironment and amber formation. We report the first Cretaceous ostracod in amber-the gigantic (12.9 mm) right valve of an exclusively marine group (Myodocopa: Myodocopida) preserved in Burmese amber. Ostracods are usually small (0.5-2 mm), with well-calcified carapaces that provide an excellent fossil record extending to at least the Ordovician (~485 million years ago), but they are rarely encountered in amber. The new specimen effectively doubles the age of the ostracod amber record, offering the first representative of the Myodocopa, a weakly calcified group with a poor fossil record. Its carapace morphology is atypical and likely plesiomorphic. The preserved valve appears to be either a moulted exuvium or a dead and disarticulated specimen, and subsequent resin flows contain forest floor inclusions with terrestrial arthropods, i.e., fragmentary remains of spiders, and insect frass. These features resolve an enigmatic taphonomic pathway, and support a marginal marine setting for resin production.
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http://dx.doi.org/10.1038/s41598-018-19877-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5778021PMC
January 2018

Contributions to the palaeofauna of Ptinidae (Coleptera) known from Baltic amber.

Zootaxa 2017 Nov 6;4344(1):181-188. Epub 2017 Nov 6.

Institute of Life Sciences and Technologies, Daugavpils University, Vienības Str. 13, Daugavpils, LV-5401, Latvia..

Hemicoelus favonii sp. nov. is described and illustrated from Eocene Baltic amber. This new fossil species differs from extant congeners in having 11-segmented antennae; a metathoracic ventrite with large impression in its anterior portion; a pronotum distinctly narrower than the elytral base region; the posterior suture of abdominal ventrite 1 weakly arcuate medially; sharp lateral pronotal margins that are incomplete and distinct in their basal half only; elytral striae that are not grouped in pairs; posterior pronotal angles that are rounded; elytral intestriae 3, 5, 7 and 9 that are distinctly convex; and a comparatively small total body size. The presence of Hemicoelus in Baltic amber suggests that moist, rotting wood was available as a microhabitat in the ancient forest. Beyond the new species description, the systematic placement of Anobium jacquelinae Hawkeswood, Makhan & Turner is discussed. A new fossil record for Microbregma waldwico Bukejs & Alekseev, and the first report of the genus Trichodesma LeConte from Eocene Baltic amber are also presented.
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http://dx.doi.org/10.11646/zootaxa.4344.1.12DOI Listing
November 2017

Response to: Phylogenetic placement, developmental trajectories and evolutionary implications of a feathered dinosaur tail in Mid-Cretaceous amber.

Curr Biol 2017 03;27(6):R216-R217

Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.

In his correspondence, Markus Lambertz [1] raises some concerns about the phylogenetic placement and feather development of DIP-V-15103, the amber-entombed tail section that we recently reported [2] as fragmentary remains of a non-pygostylian coelurosaur (likely within the basal part of Coelurosauria). We here would like to respond to these concerns.
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http://dx.doi.org/10.1016/j.cub.2017.02.023DOI Listing
March 2017

A Feathered Dinosaur Tail with Primitive Plumage Trapped in Mid-Cretaceous Amber.

Curr Biol 2016 12 8;26(24):3352-3360. Epub 2016 Dec 8.

Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada.

In the two decades since the discovery of feathered dinosaurs [1-3], the range of plumage known from non-avialan theropods has expanded significantly, confirming several features predicted by developmentally informed models of feather evolution [4-10]. However, three-dimensional feather morphology and evolutionary patterns remain difficult to interpret, due to compression in sedimentary rocks [9, 11]. Recent discoveries in Cretaceous amber from Canada, France, Japan, Lebanon, Myanmar, and the United States [12-18] reveal much finer levels of structural detail, but taxonomic placement is uncertain because plumage is rarely associated with identifiable skeletal material [14]. Here we describe the feathered tail of a non-avialan theropod preserved in mid-Cretaceous (∼99 Ma) amber from Kachin State, Myanmar [17], with plumage structure that directly informs the evolutionary developmental pathway of feathers. This specimen provides an opportunity to document pristine feathers in direct association with a putative juvenile coelurosaur, preserving fine morphological details, including the spatial arrangement of follicles and feathers on the body, and micrometer-scale features of the plumage. Many feathers exhibit a short, slender rachis with alternating barbs and a uniform series of contiguous barbules, supporting the developmental hypothesis that barbs already possessed barbules when they fused to form the rachis [19]. Beneath the feathers, carbonized soft tissues offer a glimpse of preservational potential and history for the inclusion; abundant Fe suggests that vestiges of primary hemoglobin and ferritin remain trapped within the tail. The new finding highlights the unique preservation potential of amber for understanding the morphology and evolution of coelurosaurian integumentary structures.
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http://dx.doi.org/10.1016/j.cub.2016.10.008DOI Listing
December 2016

Passandra septentrionaria sp. nov.: the first described species of Passandridae (Coleoptera: Cucujoidea) from Eocene Baltic amber.

Zootaxa 2016 Jul 26;4144(1):117-23. Epub 2016 Jul 26.

Royal Saskatchewan Museum, 2445 Albert St., Regina, SK S4P 4W7, Canada.; Email:

Based on two relatively well-preserved specimens from Eocene Baltic amber, Passandra septentrionaria sp. nov. is described and illustrated. It is the first formally described species of Passandridae from Baltic amber, and the first known European representative of the family. The global distribution of extant Passandra Dalman is mapped, and the historical distribution of the group is briefly discussed.
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http://dx.doi.org/10.11646/zootaxa.4144.1.7DOI Listing
July 2016

Mummified precocial bird wings in mid-Cretaceous Burmese amber.

Nat Commun 2016 06 28;7:12089. Epub 2016 Jun 28.

Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China.

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans.
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http://dx.doi.org/10.1038/ncomms12089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4931330PMC
June 2016

Pristine Early Eocene wood buried deeply in kimberlite from northern Canada.

PLoS One 2012 19;7(9):e45537. Epub 2012 Sep 19.

Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada.

We report exceptional preservation of fossil wood buried deeply in a kimberlite pipe that intruded northwestern Canada's Slave Province 53.3±0.6 million years ago (Ma), revealed during excavation of diamond source rock. The wood originated from forest surrounding the eruption zone and collapsed into the diatreme before resettling in volcaniclastic kimberlite to depths >300 m, where it was mummified in a sterile environment. Anatomy of the unpermineralized wood permits conclusive identification to the genus Metasequoia (Cupressaceae). The wood yields genuine cellulose and occluded amber, both of which have been characterized spectroscopically and isotopically. From cellulose δ(18)O and δ(2)H measurements, we infer that Early Eocene paleoclimates in the western Canadian subarctic were 12-17°C warmer and four times wetter than present. Canadian kimberlites offer Lagerstätte-quality preservation of wood from a region with limited alternate sources of paleobotanical information.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0045537PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3446892PMC
March 2013

New and revised maimetshid wasps from Cretaceous ambers (Hymenoptera, Maimetshidae).

Zookeys 2011 24(130):421-53. Epub 2011 Sep 24.

CNRS UMR 6118 Géosciences and Observatoire des Sciences de l'Univers de Rennes, Université Rennes 1, Campus de Beaulieu bât. 15, 263 avenue du Général Leclerc, 35042 Rennes Cedex, France.

New material of the wasp family Maimetshidae (Apocrita) is presented from four Cretaceous amber deposits - the Neocomian of Lebanon, the Early Albian of Spain, the latest Albian/earliest Cenomanian of France, and the Campanian of Canada. The new record from Canadian Cretaceous amber extends the temporal and paleogeographical range of the family. New material from France is assignable to Guyotemaimetsha enigmatica Perrichot et al. including the first females for the species, while a series of males and females from Spain are described and figured as Iberomaimetsha Ortega-Blanco, Perrichot & Engel, gen. n., with the two new species Iberomaimetsha rasnitsyni Ortega-Blanco, Perrichot & Engel, sp. n. and Iberomaimetsha nihtmara Ortega-Blanco, Delclòs & Engel, sp. n.; a single female from Lebanon is described and figured as Ahiromaimetsha najlae Perrichot, Azar, Nel & Engel, gen. et sp. n., and a single male from Canada is described and figured as Ahstemiam cellula McKellar & Engel, gen. et sp. n. The taxa are compared with other maimetshids, a key to genera and species is given, and brief comments made on the family.
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http://dx.doi.org/10.3897/zookeys.130.1453DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3260773PMC
August 2012

A diverse assemblage of Late Cretaceous dinosaur and bird feathers from Canadian amber.

Science 2011 Sep;333(6049):1619-22

Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada.

The fossil record of early feathers has relied on carbonized compressions that lack fine structural detail. Specimens in amber are preserved in greater detail, but they are rare. Late Cretaceous coal-rich strata from western Canada provide the richest and most diverse Mesozoic feather assemblage yet reported from amber. The fossils include primitive structures closely matching the protofeathers of nonavian dinosaurs, offering new insights into their structure and function. Additional derived morphologies confirm that plumage specialized for flight and underwater diving had evolved in Late Cretaceous birds. Because amber preserves feather structure and pigmentation in unmatched detail, these fossils provide novel insights regarding feather evolution.
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http://dx.doi.org/10.1126/science.1203344DOI Listing
September 2011

Insect outbreaks produce distinctive carbon isotope signatures in defensive resins and fossiliferous ambers.

Proc Biol Sci 2011 Nov 23;278(1722):3219-24. Epub 2011 Mar 23.

Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta, Canada.

Despite centuries of research addressing amber and its various inclusions, relatively little is known about the specific events having stimulated the production of geologically relevant volumes of plant resin, ultimately yielding amber deposits. Although numerous hypotheses have invoked the role of insects, to date these have proven difficult to test. Here, we use the current mountain pine beetle outbreak in western Canada as an analogy for the effects of infestation on the stable isotopic composition of carbon in resins. We show that infestation results in a rapid (approx. 1 year) (13)C enrichment of fresh lodgepole pine resins, in a pattern directly comparable with that observed in resins collected from uninfested trees subjected to water stress. Furthermore, resin isotopic values are shown to track both the progression of infestation and instances of recovery. These findings can be extended to fossil resins, including Miocene amber from the Dominican Republic and Late Cretaceous New Jersey amber, revealing similar carbon-isotopic patterns between visually clean ambers and those associated with the attack of wood-boring insects. Plant exudate δ(13)C values constitute a sensitive monitor of ecological stress in both modern and ancient forest ecosystems, and provide considerable insight concerning the genesis of amber in the geological record.
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http://dx.doi.org/10.1098/rspb.2011.0276DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3169029PMC
November 2011

A new proposal concerning the botanical origin of Baltic amber.

Proc Biol Sci 2009 Oct 1;276(1672):3403-12. Epub 2009 Jul 1.

Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada.

Baltic amber constitutes the largest known deposit of fossil plant resin and the richest repository of fossil insects of any age. Despite a remarkable legacy of archaeological, geochemical and palaeobiological investigation, the botanical origin of this exceptional resource remains controversial. Here, we use taxonomically explicit applications of solid-state Fourier-transform infrared (FTIR) microspectroscopy, coupled with multivariate clustering and palaeobotanical observations, to propose that conifers of the family Sciadopityaceae, closely allied to the sole extant representative, Sciadopitys verticillata, were involved in the genesis of Baltic amber. The fidelity of FTIR-based chemotaxonomic inferences is upheld by modern-fossil comparisons of resins from additional conifer families and genera (Cupressaceae: Metasequoia; Pinaceae: Pinus and Pseudolarix). Our conclusions challenge hypotheses advocating members of either of the families Araucariaceae or Pinaceae as the primary amber-producing trees and correlate favourably with the progressive demise of subtropical forest biomes from northern Europe as palaeotemperatures cooled following the Eocene climate optimum.
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http://dx.doi.org/10.1098/rspb.2009.0806DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817186PMC
October 2009
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